封冻河道中桥墩附近流场的数值模拟

发布时间：2018-02-04 12:18

本文关键词： 封冻期单排桥墩双排桥墩流场分析数值模拟　出处：《合肥工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：冰塞是指冰花或者碎冰在河道中聚集的现象，聚集停滞的冰块由于拥挤作用使水面流冰堵塞形成冰盖，冰盖的形成使水流的湿周增大，水流将冰块浮起，水流流速减小，，过水断面增大，引起水位上升，这是冰塞对河流的一种影响，而跨河桥梁及其墩台的存在改变了河道中原有的冰塞水力特性，对河流的挤压为冰块的聚集提供了有利条件，加剧了河道中桥梁的安全威胁。冰盖下的桥墩局部冲刷是造成桥梁破坏失事的重要原因之一，对于桥墩周围水流流态的研究有助于对桥墩局部冲刷的研究。目前国内外许多学者和科技工作者进行了大量室内明渠水槽模型试验、野外测量和数值计算的研究，研究大多集中在明渠条件下单个桥墩周围的水流特性和紊流强度的研究，对封冻河道中单排桥墩、双排桥墩的情况却研究较少。本次研究以CRREL试验水槽为模型，通过Fluent软件，基于多相流理论，建立封冻条件下桥墩附近流场的三维标准k湍流数值模型。基于不同的桥墩直径、入口水流速度以及冰厚条件，研究分析单排圆柱形桥墩与双排圆柱形桥墩在不同工况条件下对桥墩附近流场的影响及两者的区别。模拟结果显示：单排圆形桥墩条件下水流对桥墩附近流场的影响比双排圆形桥墩条件更加强烈，桥墩附近的流速也相应的更大；封冻条件下入口水流速度越大对桥墩的冲刷越严重；冰盖厚度越大桥墩附近的动水压力越大，对桥墩冲刷越大；圆柱形桥墩直径越大，对河道过水断面的压缩越大，桥墩周围的流速越大，对桥墩冲刷也就越大。与CRREL水槽试验所得数据相比较，数值模拟研究得到的规律基本符合实验规律。
[Abstract]:Ice plug refers to the phenomenon that ice flowers or broken ice gather in the river channel. Because of the crowded ice, the ice sheet is blocked by the ice flow on the surface of the water. The formation of the ice sheet increases the wet cycle of the water flow, and the flow of ice floats up the ice block. The flow velocity decreases and the cross section increases, which causes the water level to rise, which is a kind of influence of the ice plug on the river, and the existence of bridge beam and its pier has changed the original hydraulic characteristics of the ice slug in the river. The compression of the river provides a favorable condition for the accumulation of ice and intensifies the safety threat of the bridge in the river. The local scour of the pier under the ice cover is one of the important reasons for the damage and failure of the bridge. The study of the water flow around the pier is helpful to the study of the local scour of the pier. At present, a large number of indoor open channel flume model tests have been carried out by many scholars and scientists at home and abroad. The research of field measurement and numerical calculation mostly focuses on the characteristics of water flow and turbulence intensity around a single pier under open channel conditions, but less on the case of single row pier and double row pier in frozen channel. In this study, the CRREL experimental flume is used as the model, and the multiphase flow theory is based on the Fluent software. A three-dimensional standard k turbulence numerical model of flow field near the pier under frozen conditions is established based on different pier diameters, inlet flow velocity and ice thickness conditions. The effects of single row cylindrical pier and double row cylindrical pier on the flow field near the pier under different working conditions and their differences are analyzed. The simulation results show that:. The effect of water flow on the flow field near the pier is stronger than that under the condition of double row circular pier. The velocity of the bridge piers is also higher. Under the condition of freezing, the bigger the velocity of inlet flow is, the more serious the erosion of bridge pier is. The larger the thickness of ice cover, the greater the dynamic pressure near the pier, and the greater the scour to the pier. The larger the diameter of the cylindrical pier, the greater the compression of the river passage section, the greater the velocity of flow around the pier, and the greater the scour of the pier. Compared with the data obtained from the CRREL flume test. The law obtained by numerical simulation basically accords with the experimental law.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U442.3;TV133

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